Phenolic contents and L-phenylalanine ammonia-lyase activity in peach fruit as affected by rootstocks

Abstract

Phenolic contents in ripe fruit of six peach cultivars (Prunus persica Batsch) grafted on P. persica ('Juseito' or 'Nagano-yaseito'), P. tomentosa (Nanking cherry) or P. japonica (Japanese bush cherry) rootstocks were evaluated. In all cultivars, fruit from trees grafted on Nanking cherry contained more total phenolic compounds than did those on 'Juseito' or 'Nagano-yaseito'. However, there were wide variations in total phenolic contents among the cultivars; being low in 'Saotome', 'Yahata-hakuho', and 'Chikuma' but high in 'Sanyo-suimitsu', 'Setouchi-hakuto', and 'Golden Peach'. 'Sanyo-suimitsu'/Japanese bush cherry combination had the highest total phenolic content, compared with the same cultivar grafted on Nanking cherry or 'Juseito'. The level of higher molecular fraction of phenolic compounds was positively correlated with the total phenolic concentration. In addition, phenolic contents, L-phenylalanine ammonia-lyase (PAL) activity and L-phenylalanine content in fruit of 'Sanyo-suimitsu' trees, grafted on 'Juseito' and Nanking cherry, were investigated during fruit growth. Although the seasonal trends of total and higher molecular phenolic contents in 'Sanyo-suimitsu' grafted on 'Juseito' and Nanking cherry were similar, they were higher in Nanking cherry throughout fruit development, especially during Stage 2. PAL activity was high during Stage 1 and the first half of Stage 2, followed by a decrease to undetectable levels by harvest. During the early growth stages, higher PAL activity and lower L-phenylalanine content were found in fruit from trees on Nanking cherry than 'Juseito'.